(1) Field of the Invention
This invention relates to a means of providing controlled release of bioactive materials. More particularly, this invention relates to the preparation of alginate gel beads that contain a bioactive material dispersed therein.
(2) Description of the Prior Art
U.S. Pat. No. 4,053,627, of the prior art, describes the use of alginate gel discs to release juvenile harmone into an aqueous environment. The process requires that the salt which yields the gellant cation, such as calcium, be insoluble or almost insoluble in water, and be admixed with the alginate and a solubilizing agent. The salt must not, of itself, yield sufficient cations to gelatinize the alginic component until the solubilizing agent gradually reacts with the salt. Gel formation is relatively slow requiring a minimum of 2 hrs., during which time the mixture is kept in a mold.
U.S. Pat. No. 3,649,239 describes a fertilizer composition in an alginate carrier that is applied to soil as a liquid if the soil is acidic, and as a gel if the soil is highly alkaline. In the latter case the gel is made by incorporating an acid gellant as an ingredient in the alginate fertilizer solution. Metal ions such as calcium are used only in certain circumstances as a soil application after the fertilizer composition has been applied to the soil.